The present invention concerns supple implantable prostheses used in surgery for increasing the volume of, modifying and repairing body shapes. The main example is the breast prosthesis but the invention also concerns calf, testicle and buttock prostheses and any other prosthesis intended to replace or simulate soft tissue.
A known prosthesis comprises a deformable bag made from a biocompatible material and containing a silicone gel. In spite of its remarkable properties of suppleness and adaptation due to the fact that the silicone gel has more or less the same density and the same consistency as human soft tissue, this prosthesis is prohibited by many laws because the silicone gel passes through the bag and spreads throughout the body, where it is liable to cause serious problems.
A prosthesis similar to that which has just been described is also known, the difference being that a polysaccharide gel is used in place of the silicone gel. The drawback of this prosthesis is that, when the prosthesis is in place, the polysaccharide gel is liable to absorb water and cause undesirable swelling and then deflate along with osmotic exchange. Thus over time the volume of the breast of the patient varies.
A prosthesis comprising a bag filled with a physiological saline solution has also been proposed, with the drawback that the bag gradually empties due to the permeability of the solution through the membrane and so the prosthesis collapses, also with the drawback that the bag can empty completely if there is a leak.
In U.S. Pat. No. 3,986,213, a breast prosthesis comprising a bag filled with silicone gel is described, with the drawbacks described above, and whose density is reduced by a dispersion of glass or epoxy microspheres so as to reduce the total density of the prosthesis.
In European patent application No. 322 194 a bag containing elements sustaining a pressure and which are filled with a gas so as to obtain a damping effect is described among others with reference to FIG. 23. This damping effect can be supplemented by a structure in the form of a spring inside each element. In addition to this prosthesis being very complicated to manufacture and therefore prohibitively expensive, when the elastic force of the spring inside each element sustaining compression is added to the force due to the gas pressure inside this element, the membrane constituting the bag becomes too firm to constitute the surface of an artificial breast unless it is accepted that, when these elements burst or lose their fluid due to the permeability of the membranes which constitute them, they collapse. Then, however, the volume of the breast is not maintained.